Transfer printing processes involve physically transferring an image from one substrate to another. Transfer media are receivers for print media from which an image is subsequently transferred. Transfer media are commonly rectangular sheets in sizes such as A and A4 upon which one or more materials are coated. The transfer media may include a release layer that encourages release of the image to the substrate during transfer. The materials coated on the transfer media may be binder materials that bond the image to the final substrate upon which the image is to appear, which may be a textile.
Sublimation transfer technologies are widely used in digital printing applications. However, these applications are limited to substrates that comprise a synthetic component, such as polyester materials. Due to the characteristics of the sublimation colorants, full color sublimation transfer technology has been mainly used for white or pastel substrates. Furthermore, sublimation printing process requires relatively low to medium energy sublimation colorants, and fastness properties, especially light fastness, have been an issue for these applications.
Attempts have been made to print images on dark substrates, such as dark colored textile materials. For instance, peelable white transfer papers have been used in combination of sublimation inks. This method requires a relatively thick coating structure in order to allow mechanical separations of transfer film from supporting paper. Such a thick structure creates a heavy, and undesirable, ‘hand’ on textile substrates. In addition, film peeled from a supporting paper after imaging the film becomes dimensionally unstable, resulting in image distortion.
Sublimation printing with other forms of white transfer paper has also been used in dark fabric material printing. However, the heavy use of white pigment in the transfer layers, with the binders having high affinity to sublimation dyes, yields poor penetration and transfer efficiency, as well as low image resolution by large dot-gain, making the final product undesirable for apparel and delicate textiles when high quality or photographic quality images are required. The spread of sublimation dyes through the entire pigmented layers consumes unnecessary amount of colorants.